On the spectra and distance scale of short Gamma Ray--Bursts

Abstract

I discuss the spectral properties of short GRBs detected by BATSE and compare them with long events. The detailed modeling of short GRB spectra shows that their being (on average) harder than long events (as it has been found by comparing their hardness ratios) is indeed due to a harder low energy spectral component (i.e. the powerlaw of the Band or cutoff-powerlaw model) in short GRBs which, instead, have a peak energy similar to long events. Another open issue is the distance scale to short GRBs. While the few redshift measurements suggests that they are at z<1, statistical studies (with local galaxies or X-ray selected clusters) suggest that they should be even more local.